Optical fiber laser transmitters (i.e., packages that contain a semiconductor laser that is optically coupled to an optical fiber, typically a single mode fiber, that extends from the package) can be found in most, if not all, optical fiber communication systems. Such transmitters will almost certainly also be part of fiber-to-the-home communication systems. In view of the widespread current and future use of optical fiber laser transmitters it is important to have available a package design that can be economically and reliably manufactured and that yields a simple, thermally and mechanically stable single mode fiber transmitter package. This application discloses such a design.
The prior art knows many different transmitter designs, including many that utilize an integral resistor as heat source for solder bonding a component (typically the optical fiber) to a mounting part in the package. However, the prior art designs typically fall short of the above mentioned design goals. For instance, prior art designs typically comprise a multiplicity of piece parts, frequently including a variety of materials. Such designs typically are relatively difficult to assemble, require maintenance of close tolerances, and tend to be subject to thermal drift, due to differences in thermal expansion coefficients. Those skilled in the art will know that displacement of the, typically lensed, single mode fiber end by a mere fraction of a micron from the position of maximum coupling can result in significant loss of coupling efficiency.
Exemplary of prior art designs are U.S. Pat. Nos. 4,702,547; 4,798,439; 4,807,956; and 4,844,581; French patent publication No. 2,582,413 (publication date Nov. 28, 1986); Japanese patent 63-285,505/1988, and D. H. Hartman et al., Proceedings of SPIE, Vol. 703, p. 42 (1986). For instance, the '956 patent shows a laser (5) mounted on a base (15), with the base mounted on a substrate (13). The fiber is attached to a "sandwich" (14) on the substrate (13), with the sandwich consisting of an insulating layer (23), a resistor (24), a further insulating layer (25), and a metallic layer (26). A slit (16) provides some thermal isolation between the resistor (24) and the laser mount. As a further example, the '581 patent discloses a laser (33) mounted on a header (34) on ceramic substrate (1), and the fiber (36A) is attached by means of solder (7) to a multilayer feature (see FIG. 2 of the patent) that is disposed on substrate 1. The multilayer feature consists of screen printed thick films. Consequently, the thickness of the feature typically is difficult to control.